The city of Butler is the county seat of Butler County in the U.S. state of Pennsylvania, situated 35 miles (56 km) north of Pittsburgh. The population was 15,121 at the 2000 census.
Butler was named for Maj. Gen. Richard Butler, who fell at the Battle of the Wabash, also known as St. Clair's Defeat, in western Ohio in 1791.
In 1803 John and Samuel Cunningham became the first settlers in the village of Butler. After settling in Butler, the two brothers laid out the community by drawing up plots of land for more incoming settlers. By 1817, the community was incorporated into a borough. The first settlers were of Irish or Scottish descent and were driving westward from Connecticut. In 1802 the German immigrants began arriving, with Detmar Basse settling in Jackson Township in 1802 and founding Zelienople the following year. After George Rapp arrived in 1805 and founded Harmony, larger numbers of settlers followed. John A. Roebling settled Saxonburg in 1832, by which time most of the county was filled with German settlers.